Thermally driven device utilizable for novelty, demonstration and/or display purposes

ABSTRACT

A plurality of free pistons of substantially integral construction are provided so that one piston is located in each of a plurality of cylinders. Each of the pistons has approximately the same, but differing, natural oscillation frequencies. Means are provided to connect the cylinders in fluid flow relationship. The oscillating pistons are thermodynamically driven by energy from an incandescent light bulb so that all of them simultaneously move toward the connecting means while moving away from variable volume bounce chambers. The pistons also simultaneously move away from the connecting means. The pistons are synchronously driven by applying a sufficient differential pressure to them to cause the pistons to oscillate at the same frequency and at substantially the same phase. The differential pressure applied to the pistons is generated thermodynamically. The synchronous oscillation is maintained even though objects, such as balls or balloons, are located in one of the variable volume bounce chambers and undergo random collisions with one of the pistons. Different embodiments of a bounce chamber are disclosed to augment or modify the motion of the objects. Different embodiments of convenient starting means are disclosed to supply a pulse of fluid pressure to the pistons.

llnited States Patent [191 Schuman Sept. 2, 1975 THERMALLY DRIVEN DEVICE UTILIZABLE FOR NOVELTY, DEMONSTRATION AND/OR DISPLAY PURPOSES Mark Schuman, 101 G. St., SW. No.5 16, Washington, DC. 20024 [22] Filed: Oct. 23, 1973 [21] Appl. No.: 408,288

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 227,514, Feb. 18, 1972, Pat. No. 3,807,904, which is a continuation-in-part of Ser. No. 121,371, March 5, 1971, abandoned.

[76] Inventor:

3,807,904 4/1974 Schuman 417/207 Primary Examiner-William L. Freeh Assistant ExaminerG. P. LaPointe Attorney, Agent, or Firm-Lowe, King & Price [5 7] ABSTRACT A plurality of free pistons of substantially integral construction are provided so that one piston is located in each of a plurality of cylinders. Each of the pistons has approximately the same, but differing, natural oscillation frequencies. Means are provided to connect the cylinders in fluid flow relationship. The oscillating pistons are thermodynamically driven by energy from an incandescent light bulb so that all of them simultaneously move toward the connecting means while moving away from variable volume bounce chambers. The pistons also simultaneously move away from the connecting means. The pistons are synchronously driven by applying a sufficient differential pressure to them to cause the pistons to oscillate at the same frequency and at substantially the same phase. The differential pressure applied to the pistons is generated thermodynamically. The synchronous oscillation is maintained even though objects, such as balls or balloons, are located in one of the variable volume bounce chambers and undergo random collisions with one of the pistons. Different embodiments of a bounce chamber are disclosed to augment or modify the motion of the objects. Different embodiments of convenient starting means are disclosed to supply a pulse of fluid pressure to the pistons.

66 Claims, 2 Drawing Figures PATENTED SEP 2 I975 SHEET 1 0F 2 THERMALLY DRIVEN DEVICE UTILIZABLE FOR NOVELTY, DEMONSTRATION AND/OR DISPLAY PURPOSES RELATIONSHIP TO COPENDING APPLICATION The present application is a continuation-in-part of my copcnding application entitled Oscillating Piston Apparatus," filed Feb. 18, 1972, Ser. No. 227,514, now U.S. Pat. No. 3,807,904, granted April 30, 1974, which is a continuation-in-part of my patent application filed Oscillating Piston Apparatus." fled Mar. 5, 1971, Ser. No. 121,371, now abandoned.

BACKGROUND OF THE INVENTION In my US. Pat. No. 3,489,335, granted Jan. 13, 1970 and reissued as Re. 27,740 on Aug. 21, 1973, there is disclosed a cylinder containing a pair of synchronized, free oscillating pistons driven thermodynamically so that the two pistons simultaneously move toward each other during one portion of a cycle and move away from each other during another portion of the cycle.

In the aforementioned co-pending application, as well as my applications Ser. No. 169,003, filed Aug. 4, 1971 (now abandoned), Ser. No. 205,651, filed Dec. 7, 1971, now US. Pat. No. 3,782,859, issued Jan. 1, 1974, and Ser. No. 264,483, filed June 20, 1972, now US. Pat. No. 3,767,325, issued Oct. 23, 1973, there are disclosed similar synchronized free piston devices wherein each of the pistons oscillates in a separate cylinder, and the two cylinders are connected in fluid flow relationship by a conduit or conduits of relatively narrow cross-section compared to the cylinder crosssection. The conduits connect together one variable volume chamber of each cylinder. Ths pistons may be thermodynamically or pneumatically driven. as disclosed in FIG. 8 of Ser. No. 205,651. A similar synchro nized arrangement of thermally driven oscillating bellows is disclosed in my application, Ser. No. 241,742, filed Apr. 6, 1972, now US. Pat. No. 3,827,675, issued Aug. 6, 1974, wherein end faces of a pair of bellows oscillate synchronously and oppositely and the volumes of the bellows are connected in fluid flow relationship through a region having a cross-sectional area less than that of the bellows.

BRIEF DESCRIPTION OF THE INVENTION One application of the device is as a novelty device thermodynamically driven by heat from a radiant source such as an incandescent light bulb of a lamp. To enhance the use of the device for novelty purposes, random motion masses, e.g., rubber balls, can be placed in a bounce chamber of one of the cylinders, to be driven by a piston face.

To further enhance the novelty and other aspects of the device, two embodiments of more convenient and reliable starters are disclosed. In one of the improved starters, a pneumatic pulse is supplied to a face of one of the free pistons by a manually operated starter piston that is rapidly traversed from an enlarged diameter portion of a starter cylinder into a reduced diameter portion ofthe starter cylinder in fluid flow relation with the free piston face. Thereby, a pulse of fresh air is supplied to the face to initiate the piston oscillation. The opposite face of the free piston is exposed to air in a chamber responsive to a source of thermal energy, such as is obtained from an incandescent lamp bulb irradiating a heat and light absorbing member. In the second starter, air to provide the pneumatic pulse to the face is manually drawn into a bellows via a conduit from the interior of the thermally responsive chamber. Manual contraction of the bellows compresses the air and provides the desired pneumatic pulse to the face to initiate oscillation. The bellows has a fold that seals off the conduit during normal operation.

It is accordingly an object of the present invention to provide a new and improved novelty device including a pair of synchronized free oscillating pistons driven by heat from a lamp. wherein synchronism is maintained in spite of one or more small balls or other objects being placed in a variable volume chamber of the device to randomly bounce against or collide with one of the free pistons.

A further object of the present invention is to provide a new and improved means for starting a thermally powered free piston device.

Another object of the present invention is to provide a new and improved, thermally powered, oscillatory compressible fluid device wherein a rebound chamber of the device contains a lightweight object agitated by oscillation of the device.

Another object of the present invention is to provide a new and improved, thermally powered, oscillatory, compressible fluid device wherein a rebound chamber of the device contains an object of low density agitated by oscillation of the device, wherein heating of the rebound chamber or object augments the motion of the object.

Another object of the present invention is to provide a new and improved, thermally powered, oscillatory, compressible fluid device wherein a rebound chamber is designed to augment or modify the motion of the object.

The above and still further objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description of several specific embodiments thereof, especially when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic, elevational, cross-sectional view of a free piston novelty device wherein heat and light from an incandescent electric light bulb are absorbed by a passageway means which is connected by a glass tee to a pair of synchronized free pistons oscillating in glass cylinders; also shown in FIG. 1 is a novel starting means, as well as bouncing balls or balloons in an upper rebound chamber;

FIG. 2 is a schematic, clevational, crosssectional view of a second embodiment of a free piston novelty device in which the upper rebound chamber is shaped to form a pneumatic circuit in which the balls travel, and a novel bellows type starting device for initiating the piston oscillation is illustrated;

DETAILED DESCRIPTION OF THE DRAWING Reference is now made to FIG. 1 wherein there is illustrated a device including two thermally driven free pistons 1a and lb oscillating synchronously and oppositely in vertical, in-line cylinders 2a and 2b, as similarly described in my copending application Ser. No. 227,514. The pistons oscillate between compressible fluid or gaseous springs comprising variable volume rebound or bounce chambers 3a and 312 above and below pistons la and 1h. Chambers 3a and 3b reverse the motion of the pistons and drive the pistons simultaneously toward each other and toward a common, variable volume, central chamber comprising heated passageways 4a and 4b to which variable volume chambers 50 and 5b of cylinders and 2b are connected in fluid flow relationship by tee 6. ln-line 7a and 7b of tee 6, which generally are of equal length and bore, pneumatically connect chambers 5a and 5b to common arm 7(' of tee 6 which, in turn, connects arms 7a and 7b of the tee with passageways 4a and 4b of heated passageway means or chamber 8. Thus, the flow of compressible fluid (air) into and out of passageways 4a and 4b is combined in arm 70.

Heating chamber 8 is cupor Dewar-shaped to fit over the top of and absorb most of the heat and at least some of the radiant energy or light from incandescent, electric light bulb 9 mounted in light bulb socket 10, which can be connected via a voltage reducer to a conventional 60 Hertz, 120 volt electrical outlet to provide power to operate the light bulb. A voltage reducer, such as a dimmer switch or triac, is preferable to prolong the life of the bulb under these slightly unusual operating conditions. Bulb 9 fits through a central hole in plate 11 which is supported by means not shown and provides support for passageway means 8. Plate 11 also provides thermal insulation and reflects light from bulb 9 upward for partial absorption within chamber 8 and partial light transmission and scattering through chamber 8 into a room in which the device is located to augment illumination of the room by the lamp. As disclosed in Ser. No. 227,514, the walls of chamber 8 may be made of colored glass, such as colored Pyrex, to absorb light for conversion into heat to drive the pistons and to transmit or provide colored light. Alternatively, the internal surface 44 of chamber 8 and especially the walls of passageways 4a and 4!? may be coated with a thin layer of radiation and light absorbing and reflect ing, and perhaps colored, substance. This has the advantage of converting radiation into heat at points closest to the gas to be heated in passageway means 8 and relatively far, and therefore thermally relatively well insulated, from the cool environment outside of chamber 8, for more efficient conversion of the light into amplitude of piston oscillation, and therefore greater efficiency of thermodynamically converting electrical power into piston oscillation via an electrically driven radiant sourcev Another advantage of coating internal surfaces of the passageways 4 with absorbing substances is that the temperature of the bulb is cooler for a given passageway surface temperature, to provide longer bulb life; the temperature of the outer surface of passageway means 8 is also cooler, thereby lessening the need for an optional thermal insulator/partial reflector (not shown) around the outside of chamber 8. Alternatively, the glass walls can be frosted, again preferably or especially on the internal surfaces of the passageways 4, i.e., a thin frosted layer on the walls of passageways 4, to absorb, reflect, and scatter the light (or radiant energy) in order to make chamber 8 a more diffuse and therefore, aesthetically pleasing light source, as well as to increase the optical path length and ab sorption of the light in the glass, for greater conversion of the light into heat, especially on the internal surfaces of passageway means 8 where'heat is needed most and- /or where thermal insulation from the periphery of Lil chamber 8 is relatively high. The coatings mentioned above preferably absorb non-visible radiation more strongly than they absorb visible radiation. In addition, dichroic coatings can be used, especially around the outside of chamber 8, to reflect primarily non-visible or thermal radiation inward for absorption and conversion into heat.

During operation, the pistons la and 1b oscillate synchronously toward each other and then away from each other, approximately in phase. As the pistons move toward each other, compressing gas in the central or common chamber comprising passageways 4, cylinder chambers 5, and tee 6, gas is forced from the relatively cool cylinder chambers 5 into the heated passageways 4 via tee 6. The passageways 4 are relatively wide compared to heat exchanger passageways that might be designed for external combustion engines operating at the same frequency, whereby the heating of the cool gas forced by the pistons into thermal lag heating passageways 4 is relatively slow and continuous and continues appreciably even after the pistons rebound and are beginning to move apart. As pistons la and 11) start to move away from each other, heated air flows from tee 6 into the connected cylinder chambers 5 and the air in chambers 5a and 5b is cooled by the increased effective exposure of variable volume thermal lag cooling chambers formed by the proximate piston faces and cylinder side walls and end walls which in turn are exposed to the environment and ambient air for cooling. Thus, the fluid in the central or common chamber is variably or alternately exposed to the hot surfaces of the heated passageway means and the cool surfaces within the connected variable volume cylinder chambers as a result of the oscillatory synchronized piston motion. Because of the thermal lag heating and cooling effect, resulting from the wide heated passageways 4 and the wide cool cylinder chambers 5, maximum pressure and maximum average gas temperature of the gas in the central chamber are reached after pistons 1 have begun to move apart after reaching maximum instantaneous geometrical compression ratio, thereby providing pneumatic energy to drive the pistons apart and make up for frictional, thermal, and vibrational energy losses. Because of the wide cylinder chambers 5 in conjunction with the wide heated passageways 4, net cooling of the gas in the central chamber continues for a small fraction of a cycle after the pistons I reach maximum separation and begin moving toward each other, whereby minimum temperature and pressure in the central chamber are reached shortly after the pistons 1 start moving toward each other. Thus, the average pressure in the central chamber is greater during the half cycle that the pistons are moving apart than during the half cycle that the pistons are moving together, and thus the gas in the central chamber does work on the pistons to overcome losses elsewhere and sustain oscillation. Therefore, cylinder chambers 5 may be considered as drive chambers. Losses include piston-cylinder friction and leakage, as well as viscous and thermal losses in bounce chambers 3.

The centers of oscillation of pistons l are determined by axial grooves 14a and 14b in the inside surface of cylinders 2. As described in Ser. No. 227,514, these grooves serve as integral (no moving parts) cylinder bypasses which control the relative amounts of gas in the three gaseous regions and thus the center points of piston oscillation.

When bulb 9 is turned off, chamber 8 gradually cools, piston amplitude slowly decreases, and oscillation finally stops, usually within a minute or so but depending on temperatures and design. Pistons 1 then gradually settle by leakage to the bottoms of cylinders 2. Stops a and 15b are respectively provided at the top and bottom of cylinders 2a and 2b to prevent the pistons from entering bounce chambers 3. To restart the device, manually operated starter 20, which is connected to lower bounce chamber 31) via conduit 21, may be used. Starter piston 22 in starter cylinder 23 is kept at the end of cylinder 23 closest to rebound chamber 31) during operation of the novelty device and, by virtue of O-ring 24, closes and seals cylinder 23 proximate conduit 21 and thus prevents leakage of gas from bounce chamber 3b and conduit 21 out through the starter housing. To start the device, more air is generally needed in chamber 3b to raise piston lb up from its resting place above stop 15b. To obtain this air, starter piston 22 can be moved almost to the end of starter cylinder 23 farthest from bounce chamber 3b by handle 25 which extends out of cylinder 23 via a port 26 in cylinder back plate 27 at the end of cylinder 23 furthest from bounce chamber 3b. Back plate 27 has a filter 28 to allow filtered air to flow around piston 22 to fill the partial vacuum created in bounce chamber 3b and the portion ofcylinder 23 between piston 22 and the bounce chamber when the piston is moved away from the bounce chamber. The filter precludes dust and other matter above a given size range from entering the device. To facilitate this flow of filtered air around piston 22, the bore of cylinder 23 has an enlarged diameter over a portion 29 of its length proximate back plate 27 relative to the diameter of the cylinder portion 30 proximate conduit 21. Thereby, there is only a loose fit between O-ring 24 and cylinder 23 over the enlarged left end portion of the cylinder, to facilitate equalization of the pressure in the bounce chamber with the pressure in the external environment when piston 22 is proximate the left end of the cylinder, and a tight seal exists proximate the right end of the cylinder.

When starter piston 22 is manually moved rapidly toward bounce chamber 3/; by piston handle 25 to start the device, very little air has time to leak around O-ring 24 toward filter 28 while the piston is traveling in the loose fit portion 29 of cylinder 23. Piston 22 soon reaches the sealing fit portion 30 of cylinder 23 proximate conduit 21 and bounce chamber 319 and is stopped at the end of cylinder 23 closest to conduit 21 and is maintained in this position during operation of the oscillating free piston device. Thus, piston 22 and cylinder 23 provide means for connecting bounce chamber 3b in a fluid flow relationship with the external environment and for sealing and unsealing this connection. Means (now shown) can be provided for maintaining the starter piston in situ if the friction between the O-ring 24 and cylinder 23 is insufficient to hold the starter piston Proximate conduit 21. The rapid movement of starter piston 22 toward conduit 21 forces air from cylinder 23 into bounce chamber 319 via conduit 21 to pressurize the bounce chamber and provide a pneumatic impulse that rapidly raises piston 11) from its resting place on ledge 1519, which piston in turn provides a pneumatic impulse to raise piston 1a from its resting place at the bottom of cylinder 2:: and top of conduit 7a of tee 6. The pistons I tend to overshoot upward as a result of this starting impulse and rebound downward, all at a differing and changing relative phase. When the pistons begin moving oppositely, energy is provided by the heating-cooling mechanism described above, whereby the amplitude of the piston oscillation rapidly increases and the relative phase of the pistons is automatically corrected toward the steady state condition of equal and opposite motion of the two pistons. The two free pistons of one actual device similar to that illustrated normally oscillate at frequencies on the order of 5 Hertz after starting and, if the heating chamber has been fully warmed, the pistons generally within a few seconds after starting reach an amplitude and frequency within a factor of two of the steady state amplitude and frequency.

Pistons l, which are integral (contain essentially no parts moving relative to each other) and have the same cross-sectional dimensions and area throughout their length, are automatically phased so that they simultaneously move toward each other and tee 6, stop at about the same time proximate the bottom and top of cylinders 2a and 2b (respectively), then move away from each other and tee 6 at similarly changing speeds and similar magnitudes of acceleration, stop at about the same time proximate the top and bottom of cylinders 2a and 2b, and then move toward each other again with similar speeds and with similar magnitudes of acceleration to repeat the cycle. Since the cylinders 2 are in-line or along the same axis the pneumatic forces on the device induced by the synchronized pistons are substantially equal and opposite, substantially eliminating any tendency of these forces to cause the device to vibrate.

Although the gas volumes, flow impedances, and piston geometries and masses are generally matched or otherwise adjusted so that the natural or resonant frequencies of the pistons oscillating in the device are substantially the same, the matching cannot, of course, be perfect. For example, piston-cylinder friction may be greater for one piston than the other. Also, the two free pistons of the device actually constructed differ in weight by about 2% but the device starts easily and operates synchronously with minimal vibration, and does so no matter which piston is on top. Due to gravity and the weight of the pistons, the central gas chamber has a higher average pressure than the upper bounce chamber 31:, while the lower bounce chamber 31) has a still higher pressure, which tends to produce a higher spring constant for the lower piston and make it oscillate at a higher frequency. Oscillation at the higher frequency however, does not occur. In addition, the actual device starts fairly easily and synchronism between the pistons is maintained even with two very small rubber balls which are present in the cylinder chamber above the upper piston and which repeatedly collide with the upper piston, as do rubber balls 31 and 32 in bounce chamber 3a of FIG. 1.

Reference is now made to FIG. 2 in which is illustrated a free piston novelty device which is essentially identical to the embodiment of FIG. 1 except in three respects.

The first of the three differences involves the means for connecting variable volume cylinder chambers 5 to each other and to heated passageway means 8 for synchronizing the pistons 1 and providing power to sustain their oscillation. Instead of first connecting the cylinder chambers 5 to each other and then connecting chamber 8 to the mid-point of the first connecting means, as

is done in FIG. 1 by means of tee 6, cylinder chambers a and 5b in FIG. 2 are respectively connected directly to heated passageways 4a and 4b of chamber 8 by conduits 41a and 41b. At the opposite side of chamber 8 from where conduits 41a and 4112 respectively connect to passageways 4a and 4b, i.e., on the side of light bulb 9 opposite cylinders 2, a port 42 is provided in wall 43 separating cup-shaped passageways 4a and 412; port 42 joins heated passageways 4 and thereby connects cylinder chambers 5 in a fluid flow relationship as required for synchronizing pistons The second difference of FIG. 2 relative to FIG. 1

concerns an alternative sealed starter 45 comprising bellows 46. Bellows 46 is closed at its bottom end by plate 47 and has a mouth at its top end connected in fluid flow relationship with the bottom chamber 481) of cylinder 21;. During normal operation, the folds of bellows 46 are securely closed in by metal or plastic clip or snapping device 49 which holds bellows plate 47 in an upward position. Small bore conduit or cylinder bypass 50 connects port 51 in cylinder 2b with port 52 in the uppermost fold or upper endplate of bellows 46. Port 51 is located in cylinder 2b at a point above the upper face of piston lb when the device is not operating and piston lb is resting on ledge b. Conduit 50 thus connects cylinder chamber 5!; with the interior of bellows 46 while the piston I1; is resting on stop 15]) and only upon manual release of spring clip 49 and bellows plate 47, which allows bellows 46 to expand downward to allow bellows fold 53, just below port 52 and pressing against port 52, to move downward and away from port 52, thereby unblocking port 52 and conduit 50. The expansion of bellows 46 draws compressible fluid or gas or air from cylinder chamber Shinto the interior of bellows 46 which, in conjunction with cylinder chamber 48b serves as bounce chamber 55b for oscillating piston lb. This air drawn into bounce chamber 551) when bellows 46 is expanded replaces air or gas which previously leaked from chamber 55!: upward around piston lb as the piston very slowly settled downward by gravity to ledge 15/2. The previous leakage of air upward around piston 11) occurred after the pistons last stopped oscillating in response to cooling and contraction of gas in chamber 8 resulting from deactivation of electric bulb 9. Thus, when bellows 46 is lowered, sufficient air for starting enters chamber 55]) slowly via conduit 50 and chamber 512. When bellows plate 47 is suddenly pushed upward to start the device, very little air leaks through conduit 50 because of its small bore and because of the proximity of bellows fold 53 which moves upward and soon closes and seals or blocks port 52. If desired, a small rubber washer can be affixed to port 52 or a small rubber disc can be affixed to the top of fold 53, thereby extending conduit 50 and port 52 downward slightly or extending the upper surface of fold 53 upward slightly, so that port 52 is unblocked only when bellows 46 is fully extended. The upward impulse on piston 1!) resulting from the rapid upward movement of plate 47 initiates the piston oscillation as described in connection with FIG. 1, and plate 47 is secured in the upward position by clips 49. Although port 51 need only be slightly above piston lb when the piston is in its resting position, in order to draw air from chamber 5b into chamber 55b, port 51 as illustrated is located at the height of the middle of the bypass grooves, whereby port 51 and conduit 50 serve as a short bypass groove, to help maintain the center of piston oscillation against gravity. Alternatively port 51 could be shaped to form a full length bypass groove similar to grooves 14b. Port 51 could alternatively be located in the wall of chamber 55a or cylinder portion 48a.

The third difference between the embodiment of FIG. 2 and that of FIG. 1 concerns the shape of the upper bounce chamber. In FIG. 2, the upper bounce chamber 55a, instead of being substantially spherical except for variable volume cylinder portion 48a above piston 1a, is narrowed somewhat and elongated upward, and curves to the side and downward as it narrows, finally returning via port 57 to communicate again with bounce chamber 55a just above piston stop 15a at the top of cylinder 2a. Rebound chamber 55a thus forms a pneumatic circuit or loop, whereby balls 31 and 32 occasionally bounce sufficiently far upward in response to contact with the upper face of piston la to reach the crest 58 of chamber 55a and return to chamber 55a via the narrowed portion 59 and port 57 of re-entrant chamber 550, thereby traversing a loop or circuit. As illustrated in FIG. 2, it is not required that the upper and lower rebound chambers 55a and 55b have the same shape or, for that matter, the same volume. However, the piston masses may have to be mismatched to correct for a substantial rebound chamber volume or shape mismatch, i.e., a substantial spring constant or energy loss mismatch, so that the resonant frequencies of the pistons are substantially the same. This, of course, is also true of the FIG. 1 embodiment. However, as illustrated in FIG. 1, the device configuration may also be substantially symmetrical with respect to the heated passageway means and the connecting means.

The heated passageways 4a and 4b of FIGS. 1 and 2 are elongated passageways having an average length and an average breadth both of which are substantially greater than their average width; width is defined as the smallest dimension of the cross-sectional area of the flow path of the gas in a passageway. Thus, the separation of the walls of either of passageways 4 is its width. For example, in FIGS. 1 and 2, the width is less than 10 times the average length or breadth of the passageway.

It should be understood that the devices of FIGS. 1 and 2 can be operated with only a single thermal lag heating passageway if it is sufficiently elongated, broad, wide, and hot. The use of layers of passageways, however, as described and illustratedherein, provides heating surfaces for heating the gas which are further removed, and therefore thermally better insulated, from the cool outer environment as well as from the radiant source. Thus, the use of passageway layers, such as passageways 4a and 4b of FIG. 1, reduces heat loss and improves efficiency of the device. In addition, for a given amplitude of piston oscillation, passageway layers absorbing radiant energy primarily on their internal surfaces reduce feedback of heat to the radiant source, thereby lengthening the life of the radiant source in certain cases.

Although the cylinders in which the pistons are oscillating are normally exposed to the air and cooled primarily by convective cooling, other means such as a fan can be used to lower the cylinder and piston temperatures and improve the efficiency and lifetime of the device. Although the device can operate with any orientation of the cylinders, piston-cylinder wear is reduced substantially to zero if the cylinders are oriented vertically, which therefore generally is the preferred orientation. I have operated my thermally driven free piston device for fourteen hours without stopping; after the first hour, there was no significant change in the amplitude or center of oscillation of either of the two free pistons, which were oscillating synchronously and oppositely along approximately a common vertical axis.

One preferred material for the cylinder and piston walls is a glass, such as Pyrex, which can be ground to close tolerances, has a low coefficient of thermal expansion, and is transparent, the latter primarily for aesthetic reasons. The heating chamber and connecting means can generallybe'rpade of high temperature resistant, transparent material such-as. clear, colored or multi-colored glass. For novelty purposes the radiant source, the rubber balls in the upper bounce chamber, and any other components of the device can also be colored or multi-colored. The bounce chambers operate near ambient temperature whereby they need not be able to withstand high temperatures and can be made of transparent and/or colored material such as soft" glass or plastic.

The rubber balls do not, of course, have to be spheri cal or rubber. However, the balls must have sufficient radius of curvature over most of their surface to avoid being jammed between the piston and the cylinder. A spherical shape would avoid the jamming problem and, in addition, would have maximum tendency to bounce in less rapidly changing modes or bouncing patterns, especially in a spherical bounce chamber, such as bounce chamber 3:: of FIG. 1, or in a cylindrical or other regularly shaped bounce chamber. Rubber is a desirable material for the balls since it has high elasticity and low specific gravity to enable the ball to have a relatively large size and visibility without changing the piston speed excessively upon collision with the piston. If the ball or particle in the chamber is made sufficiently light in proportion to its fluid drag, the oscillat ing air in the bounce chamber agitates the ball, i.e., makes it visibly oscillate, especially if and where the bounce chamber is constricted. Thus, for example, stop 1511 can be extended further inward toward the axis of cylinder 2a in FIG. 1, to increase the amplitude of the alternating velocity of the air and thus the agitation or oscillation amplitude of the ball. To accentuate this os cillatory motion of a ball due to air drag and oscillating action, a hollow ball, such as a miniature ping pong ball, or miniature balloon, may be used; the latter is preferable because it is more silient, resilient and generally of lower density. The substance of which the ball is made should be resistant to pulverizing into smaller particles which could jam and stop the oscillating free piston.

A screen or conduit or other constriction, such as mentioned above in connect with stop 150, can be used if desired in the bounce chamber between the balls and the piston to avoid piston-ball collisions. The bores of such constricting means would then have to be smaller than the diameters of the balloons. In such a case, agi tation by the oscillating air effect mentioned above would be the primary means for inducing motion of the balls or balloons whereby the motion would be primary oscillatory. However, if the balloons are light enought, they may also drift around considerably in the bounce chamber, following currents of air. The drifting effect or motion would be accentuated if the balloons were colored to absorb light and infrared radiation from bulb 9 and chamber 8 or from another radiant source. The adsorption of light makes the balloons warmer, whereby the expand and become more buoyant. For this purpose, the bounce chamber containing the balloons can be positioned close to chamber 8 and bulb 9 so that they absorb more light. Differential heating of the balloons by bulb 9 occurs, i.e., greater heating on the side of the balloons facing bulb 9, and not only distorts a balloon slightly but also heats and imparts kinetic energy to gas molecules proximate the balloon surface, tending to make the balloon translate and rotate. Rotation is more easily perceived by a viewer if the coloring or design on the balloon has an appropriate pattern or structure, e.g., a black and white pattern. In addition, the differential or non-uniform radiant or convective remote heating of the bounce chamber wall and colored balloons in the bounce chamber by bulb 9 and heating chamber 8 tends to cause a circular flow of gas, balloons, and other objects of low density in the bounce chamber, i.e., upward on the hot side facing and close to chamber 8 and downward on the opposite, more remote cold side, as indicated by the arrow in re bound chamber 30 of FIG. 1. For greater aesthetic effect, a circuit shaped bounce chamber similar to chamber 55a of FIG. 2 can be used to channel and accentuate such circular currents and circular motion. Balloons flowing in such a circular pattern occasionally collide with the chamber wall, which imparts rotational motion to the balloons relative to the chamber wall. Another way of producing circular currents and circular motion of balloons within the bounce chamber is to use an assymetric bounce chamber or a deflector in the bounce chamber. For example, if chamber 3a were tilted or distorted a small amount in a sideways direction, balls bouncing up from piston la would tend to bounce against one side of the chamber and be deflected in a slightly preferred direction and also would, as a result of the deflection, tend to have a characteristic angular velocity about their own axes, as well as about the center of the chamber 3a. Circular motion of the balls, balloons and air can be induced by the effects of the assymetric chambers or internal deflecting surfaces. Balls and balloons can be used together so as to collide with each other and induce random motion, circular motion, or rotation of balloons in the bounce chamber.

Still another means of inducing circular motion in the bounce chamber is a plate formed by extending stop 15a inward to completely block off the upper end of cylinder 2a except for two large flapper valves on the plate. One of the valves would pass air only in a direction from piston la to bounce chamber 3a and the other valve would pass air only in the opposite direction. The two valves would be located on opposite sides of the cylinder axis. Thus, air would pass through the valves on alternate half cycles and, since the two valves are oppositely polarized and are separated by a finite distance, a circular motion of the air in bounce chamber 3a is induced thereby, and would be evidenced by a somewhat circular motion of any lightweight floating or buoyant loose objects, such as balloons, in chamber 3a.

If the bounce chambers of the embodiments herein are heated to serve as thermal lag heating chambers or if they are replaced by more efficient thermal lag heating chambers with elongated heated passageways, they contribute energy to help sustain piston oscillation, the

synchronous and opposite motion of the free pistons is maintained, and the tendency of the device to vibrate is substantially zero, assuming the device is symmetric or otherwise matched with respect to the two pistons. However, if the bounce chambers are heated and the central chamber is an unheated bounce chamber, the two pistons tend to oscillate synchronously and in the same direction, with maximum tendency to the device to vibrate. Thus, it appears that the two pistons tend to drive each other synchronously and in the same direction, but that this tendency can be overcome by differential pressure effects on the pistons induced by heating and cooling in the central or common chamber when the common chamber contains a thermal lag heating chamber, resulting in synchronous and opposite motions of the free pistons. Thus, connecting together and to a thermal lag heating chamber one variable volume chamber of each cylinder induces synchronized motion of the moving wall portions of the connected chambers toward and away from the heated passageways and toward and away from the connecting means as the volumes of the chambers decrease and increase. By connecting means such as illustrated in the embodiments herein, the cylinders and variable volume chambers can be oriented coaxially so that the wall portions move synchronously and oppositely (and alternately) toward and away from each other, while at the same time, in a pneumatic sense, moving synchronously toward and away from the heated passageway means and toward and away from the connecting means, whereby the tendency of the device to vibrate is reduced substantially to zero because of the equal and opposite cancelling pneumatic forces on the walls of the device. The cylinders can alternatively be oriented so that vibration tendency is maximized by suitably forming the connecting means, e.g., by curving arms 7a and 7b of tee 6 in FIG. 1 in a U-shape rather than in a straight line as illustrated.

In the embodiments illustrated herein, each of the peripheral oscillating wall portions is solid and of integral construction. A pair of liquid pistons would tend to become non-cohesive in most orientations and invariably would disintegrate in the vertical orientations illustrated in FIGS. 1 and 2. Also many liquids are flammable, toxic, or can cause an electric short circuit if a leak or break in the device occurs. For reasons such as these, a solid piston is generally preferable to a liquid piston. An integral piston, because of its lack of moving parts, is advantageous for a device such as a novelty lamp because of its simplicity of construction and its reliability, in addition to the added intrigue resulting from the simplicity. The heated passageway means, the connecting means, the rebound chambers, and the bypass means for positioning the free pistons are also integral. Thus, except for the free pistons and the starting means, the entire device is integral thereby probably making it more difficult for the uninitiated person to deduce the means for sustaining oscillation and for controlling the centers of oscillation of the free pistons. Once the device is started, the only moving parts are the free pistons.

In FIGS. 1 and 2, the movement of the peripheral wall portions or free pistons la and lb away from the passageway means 8 as the volume of the central chamber is increasing, increases the effective exposure area of the cool piston and cylinder surfaces of the cylinder chambers 5 to heated fluid within chambers 5 and thus to heated fluid within the central chamber, and the means for rebounding and driving the pistons toward the passageway means includes cooling of the fluid in the central chamber primarily by the increased exposure of the cool piston and cylinder surfaces by the moving portions which cooling causes contraction of the fluid and the tendency to lessen the pressure of the fluid in the central chainber and connected cylinder chambers as the volumes of the connected chambers are decreasing. The means for cooling gas in the central chamber primarily consists of the variable exposure of the cylinder walls by the oscillating pistons. Any practical number of pistons or pheripheral wall portions can be driven synchronously in the fashion of the two pistons of FIG. 1 or 2 by adding additional cylinders, rebound chambers, and connecting arms in parallel with the existing like components. In such configurations all pistons synchronously oscillate toward and away from the common heated passageway means. The fluid flow impedance, if substantial between any pair of the oscillating pistons or peripheral wall portions should be substantially the same for strong synchronization of an otherwise symmetric device. Either of the embodiments herein can be duplicated a desired number of times and all of the central chambers can be connected together (in fluid flow relationship) in like manner to obtain synchronous oscillation of the free pistons toward and away from the heated passageway means.

While there have been described and illustrated two specific embodiments of the invention, it will be clear that variations in the details of the embodiments specifically illustrated and described may be made without departing from the true spirit and scope of the invention as defined in the appended claims.

I claim:

1. An oscillatory compressible fluid device comprising a chamber cyclically varied in volume by an oscillating peripheral wall portion of the chamber, said chamber including a heated surface and a cooled surface in contact with the fluid, means including the os cillation of the wall portion for alternately varying the exposure of the fluid to the heated and cooled surfaces as the volume is decreased and increased by the oscillating portion, whereby the fluid is alternately heated and cooled by the respective surfaces, said heated surface being configured to heat said cooled fluid so as to produce an average pressure in the chamber while the chamber volume is increasing, which average pressure is higher than the average pressure in the chamber while the chamber volume is decreasing, means including said heating and cooling for sustaining oscillation of the portion, a rebound chamber for repeatedly reversing the direction of motion of the portion, said rebound chamber including an object within the volume of the rebound chamber undergoing motion relative to the remainder of the rebound chamber, and means including operation of the device for sustaining said relative motion.

2. The device of claim 1 wherein the object is small and lightweight, said rebound chamber containing the object being shaped to form a pneumatic circuit, said object transversing the circuit.

3. The device of claim 1 wherein the rebound chamber is formed to augment and display said relative motion.

4. The device of claim 1 wherein the means for sustaining the relative motion includes a heating means for heating the rebound chamber and the heated surface.

5. The device of claim 1 further including a radiant source for heating said heated surface and for providing light for illumination of the device and its surroundings, wherein the object contains a substance which absorbs radiant energy from the some to assist in sustaining the relative motion.

6. The device of claim 1 wherein the rebound chamber is asymmetrically l r'ped to modify said relative motion.

7. The device of claim 1 wherein the rebound chamber is formed to asymmetrically absorb energy from a radiant source to modify said relative motion; wherein saidfsource provides thermal energy for heating said heated surface.

8. The device of claim 1 wherein the object is a small resilient object of low density which is agitated by repeated collisions with the oscillating portion.

9. The device of claim 8 wherein the rebound cham ber is shaped to form a pneumatic circuit, whereby the object occasionally traverses the pneumatmic circuit.

10. The device of claim 1 wherein the rebound chamber is shaped to form a pneumatic circuit, whereby the object repeatedly traverses the pneumatic circuit.

11. The device of claim 1 wherein the object is composed primarily of rubber, whereby the object is lightweight and resilient.

12. The device of claim 11 wherein the object contains an internal cavity to further decrease the weight of the object relative to its size and resilience.

13. The device of claim 1 wherein the object contains an internal cavity, whereby the object is made lighter in weight relative to its size and resilience.

14. The device of claim 1 wherein the object is essentially a balloon.

15. The device of claim 1 wherein the oscillating portion comprises a free piston oscillating in a cylinder.

16. The device of claim 15 wherein the piston and cylinder side-walls are made primarily of glass.

17. The device of claim 15 wherein the free piston is of substantially integral construction.

18. The device of claim 17 wherein the free piston is the sole oscillating member of the device after oscillation has been initiated.

19. The device of claim 15 further including cylinder bypass means for positioning the center of oscillation of the piston.

20. The device of claim 19 wherein the bypass means is of integral construction.

21. The device of claim 19 wherein the bypass means bypasses a portion, and only a portion, of the axial length of the cylinder, said center of oscillation being maintained within or near the bypassed portion, said bypass means including a bypass passageway having a fluid flow impedance which is substantially the same for fluid flow in either direction through the bypass.

22. The device of claim 19 wherein the bypass means consists of internal groove means in the cylinder wall.

23. The device of claim 19 wherein the heat energy required for sustaining the oscillation of the free piston is provided by a lamp which heats the heated surface and provides light for illumination.

24. The device of claim 23 wherein ambient cooling of said cooled surface provides sufficient cooling for sustaining the oscillation.

25. The device of claim 15 wherein the cylinder is at least partially transparent to allow viewing of the oscillating free piston.

26. The device of claim 1 wherein the variable volume chamber further includes another oscillating peripheral wall portion oscillating in synchronism with the first portion so that the two portions substantially with the same phase alternately decrease and increase the volume of the chamber and cause the alternate heating and cooling of the fluid by said surfaces, and another rebound chamber for repeatedly reversing the direction of motion of the another portion.

27. The device of claim 26 wherein each of the portions is a free piston oscillating in a cylinder.

28. The device of claim 27 wherein the object is resilient and is maintained substantially in constant motion by repeated collisions with the free piston reversed in direction by the rebound chamber in which the object is located, said object being sufficiently lightweight to preclude de-synchronization of the pistons as a result of the collisions.

29. The combination of claim 27 wherein the object is a small object and is agitated by the oscillation of the free piston reversed in direction by the rebound chamber in which the object is located.

30. The combination of claim 29 wherein the rebound chamber in which the object is located is formed to have a re-entrant path to carry the object in a circuitous path.

31. The device of claim 27 wherein each of the free pistons is of substantially integral construction.

32. The device of claim 31 wherein the free pistons constitute the only oscillating members of the device after oscillation has been initiated.

33. The device of claim 31 wherein the free pistons constitute the only oscillating; members of the device after oscillation has been initiated.

34. The device of claim 31 further including means for positioning the center of oscillation of each piston in its cylinder.

35. The device of claim 34 wherein the positioning means for each cylinder comprises cylinder bypass means for bypassing a portion, and only a portion, of the axial length of the cylinder, whereby the piston is positioned near the mid-point of the bypassed portion.

36. The device of claim 35 wherein the positioning means for each piston/cylinder consists of groove means in the inside wall surface of the cylinder.

37. The device of claim 35 wherein the bypass means for each cylinder includes a cylinder bypass passageway having substantially equal fluid impedance in either direction through the passageway.

38. The device of claim 35 wherein the cylinders are arranged along a substantially common substantially vertical axis.

39. The device of claim 38 wherein the rebound chamber corresponding to the upper free piston contains said object.

40. The device of claim 34 wherein the positioning means for each cylinder is integral with the cylinder.

41. The device of claim 34 wherein the heat energy required for sustaining the oscillation is provided by a light bulb which heats the heated surface.

42. The device of claim 1 wherein the heated surface forms an elongated heated passageway communicating with said oscillating portion, said passageway having an average width and an average length which are selected in accordance with the frequency of oscillation to continuously heat said cool fluid while said cool fluid is exposed by said oscillating portion to the heated surface of said elongated heated passageway.

43. The device of claim 1 further including a radiant source for heating said heated surface and for providing light for illumination of the device and its surroundings.

44. The device of claim 43 wherein said heated surface and said device are formed so that said heating of the heated surface by said source provides sufficient heat energy for sustaining said oscillation.

45. The device of claim 44 wherein ambient cooling of said cooled surface provides sufficient cooling for sustaining the oscillation.

46. The device of claim 43 wherein a structure comprising said heated surface is formed to absorb nonvisible radiant energy from said source.

47. The device of claim 46 wherein said structure is further formed to spectrally absorb light from said source, whereby said illuminating light appears colored.

48. The device of claim 46 wherein said structure scatters and diffuses light from said source.

49. The device of claim 46 further including dichroic means for preferentially reflecting non-visible radiant energy from said source toward a piston of said structure for absorption and conversion into heat for heating said heated surface while preferentially transmitting visible radiant energy away from said structure for facilitating said illumination.

50. The device of claim 46 wherein said heated surface comprises a thin, radiant energy absorbing coating on an internal wall of said structure for converting radiant energy from said source into heat directly adjacent said fluid to be heated.

51. The device of claim 50 wherein said coating further is formed to reflect and diffuse radiant energy from said source.

52. The device of claim 46 further including a reflective surface for reflecting radiant energy from said source into said structure for absorption and conversion into heat within said structure.

53. The device of claim 46 further including a thermal insulator/partial reflector around the periphery of said structure for facilitating said heating and said illumination.

54. The device of claim 26 wherein said alternate ex posure of said fluid to the heated and cooled surfaces arises primarily at a result of the variation in chamber volume caused by the oscillating portions.

55. The device of claim 1 further including means for heating the heated surface.

56. The device of claim 55 wherein said surface is heated substantially independently of the instantaneous phase of the oscillating portion.

57. The device of claim 1 wherein said chambers are made primarily of transparent materials to facilitate observation of the object and the internal structure of the device.

58. The device of claim 1 wherein ambient cooling of said cooled surface provides sufficient cooling for sustaining the oscillation.

59. The device of claim 1 wherein the oscillating portion comprises a free piston oscillating in a cylinder, bypass means bypassing a portion, and only a portion, of the axial length of the cylinder for positioning the center of oscillation of the free piston near the mid-point of the bypassed portion, said bypass means comprising an enlargement of the inside diameter of the cylinder in a region of the cylinder side-wall within said bypassed portion.

60. The device of claim 59 wherein said bypass means provides a greater means separation between the piston and cylinder side-walls in the bypassed cylinder portion than in an adjoining portion of said cylinder.

61. The device of claim 1 wherein the rebound chamber contains a fluid, means including the oscillation of the portion for sustaining motion of the rebound fluid, wherein the means for sustaining said relative motion of the object includes said motion of the rebound fluid.

62. The device of claim 61 further including constriction means between said object and said oscillating portion to increase the velocity of the rebound fluid, whereby said relative motion of the object is augmented.

63. The device of claim 61 wherein said motion of the rebound fluid is the primary means for sustaining said relative motion of the object.

64. The device of claim 61 further including means for inducing substantially circuitous motion of the fluid in the rebound chamber.

65. The device of claim 61 further including means for inducing substantially circuitous motion of the object in the rebound chamber.

66. The device of claim 61 further including means for inducing rotational motion of the object in the re- 

1. An oscillatory compressible fluid device comprising a chamber cyclically varied in volume by an oscillating peripheral wall portion of the chamber, said chamber including a heated surface and a cooled surface in contact with the fluid, means including the oscillation of the wall portion for alternately varying the exposure of the fluid to the heated and cooled surfaces as the volume is decreased and increased by the oscillating portion, whereby the fluid is alternately heated and cooled by the respective surfaces, said heated surface being configured to heat said cooled fluid so as to produce an average pressure in the chamber while the chamber volume is increasing, which average pressure is higher than the average pressure in the chamber while the chamber volume is decreasing, means including said heating and cooling for sustaining oscillation of the portion, a rebound chamber for repeatedly reversing the direction of motion of the portion, said Rebound chamber including an object within the volume of the rebound chamber undergoing motion relative to the remainder of the rebound chamber, and means including operation of the device for sustaining said relative motion.
 2. The device of claim 1 wherein the object is small and lightweight, said rebound chamber containing the object being shaped to form a pneumatic circuit, said object transversing the circuit.
 3. The device of claim 1 wherein the rebound chamber is formed to augment and display said relative motion.
 4. The device of claim 1 wherein the means for sustaining the relative motion includes a heating means for heating the rebound chamber and the heated surface.
 5. The device of claim 1 further including a radiant source for heating said heated surface and for providing light for illumination of the device and its surroundings, wherein the object contains a substance which absorbs radiant energy from the sorce to assist in sustaining the relative motion.
 6. The device of claim 1 wherein the rebound chamber is asymmetrically shaped to modify said relative motion.
 7. The device of claim 1 wherein the rebound chamber is formed to asymmetrically absorb energy from a radiant source to modify said relative motion; wherein said source provides thermal energy for heating said heated surface.
 8. The device of claim 1 wherein the object is a small resilient object of low density which is agitated by repeated collisions with the oscillating portion.
 9. The device of claim 8 wherein the rebound chamber is shaped to form a pneumatic circuit, whereby the object occasionally traverses the pneumatmic circuit.
 10. The device of claim 1 wherein the rebound chamber is shaped to form a pneumatic circuit, whereby the object repeatedly traverses the pneumatic circuit.
 11. The device of claim 1 wherein the object is composed primarily of rubber, whereby the object is lightweight and resilient.
 12. The device of claim 11 wherein the object contains an internal cavity to further decrease the weight of the object relative to its size and resilience.
 13. The device of claim 1 wherein the object contains an internal cavity, whereby the object is made lighter in weight relative to its size and resilience.
 14. The device of claim 1 wherein the object is essentially a balloon.
 15. The device of claim 1 wherein the oscillating portion comprises a free piston oscillating in a cylinder.
 16. The device of claim 15 wherein the piston and cylinder side-walls are made primarily of glass.
 17. The device of claim 15 wherein the free piston is of substantially integral construction.
 18. The device of claim 17 wherein the free piston is the sole oscillating member of the device after oscillation has been initiated.
 19. The device of claim 15 further including cylinder bypass means for positioning the center of oscillation of the piston.
 20. The device of claim 19 wherein the bypass means is of integral construction.
 21. The device of claim 19 wherein the bypass means bypasses a portion, and only a portion, of the axial length of the cylinder, said center of oscillation being maintained within or near the bypassed portion, said bypass means including a bypass passageway having a fluid flow impedance which is substantially the same for fluid flow in either direction through the bypass.
 22. The device of claim 19 wherein the bypass means consists of internal groove means in the cylinder wall.
 23. The device of claim 19 wherein the heat energy required for sustaining the oscillation of the free piston is provided by a lamp which heats the heated surface and provides light for illumination.
 24. The device of claim 23 wherein ambient cooling of said cooled surface provides sufficient cooling for sustaining the oscillation.
 25. The device of claim 15 wherein the cylinder is at least partially transparent to allow viewing of the oscillating free piston.
 26. The device of claim 1 wherein the variable volume chamber Further includes another oscillating peripheral wall portion oscillating in synchronism with the first portion so that the two portions substantially with the same phase alternately decrease and increase the volume of the chamber and cause the alternate heating and cooling of the fluid by said surfaces, and another rebound chamber for repeatedly reversing the direction of motion of the another portion.
 27. The device of claim 26 wherein each of the portions is a free piston oscillating in a cylinder.
 28. The device of claim 27 wherein the object is resilient and is maintained substantially in constant motion by repeated collisions with the free piston reversed in direction by the rebound chamber in which the object is located, said object being sufficiently lightweight to preclude de-synchronization of the pistons as a result of the collisions.
 29. The combination of claim 27 wherein the object is a small object and is agitated by the oscillation of the free piston reversed in direction by the rebound chamber in which the object is located.
 30. The combination of claim 29 wherein the rebound chamber in which the object is located is formed to have a re-entrant path to carry the object in a circuitous path.
 31. The device of claim 27 wherein each of the free pistons is of substantially integral construction.
 32. The device of claim 31 wherein the free pistons constitute the only oscillating members of the device after oscillation has been initiated.
 33. The device of claim 31 wherein the free pistons constitute the only oscillating members of the device after oscillation has been initiated.
 34. The device of claim 31 further including means for positioning the center of oscillation of each piston in its cylinder.
 35. The device of claim 34 wherein the positioning means for each cylinder comprises cylinder bypass means for bypassing a portion, and only a portion, of the axial length of the cylinder, whereby the piston is positioned near the mid-point of the bypassed portion.
 36. The device of claim 35 wherein the positioning means for each piston/cylinder consists of groove means in the inside wall surface of the cylinder.
 37. The device of claim 35 wherein the bypass means for each cylinder includes a cylinder bypass passageway having substantially equal fluid impedance in either direction through the passageway.
 38. The device of claim 35 wherein the cylinders are arranged along a substantially common substantially vertical axis.
 39. The device of claim 38 wherein the rebound chamber corresponding to the upper free piston contains said object.
 40. The device of claim 34 wherein the positioning means for each cylinder is integral with the cylinder.
 41. The device of claim 34 wherein the heat energy required for sustaining the oscillation is provided by a light bulb which heats the heated surface.
 42. The device of claim 1 wherein the heated surface forms an elongated heated passageway communicating with said oscillating portion, said passageway having an average width and an average length which are selected in accordance with the frequency of oscillation to continuously heat said cool fluid while said cool fluid is exposed by said oscillating portion to the heated surface of said elongated heated passageway.
 43. The device of claim 1 further including a radiant source for heating said heated surface and for providing light for illumination of the device and its surroundings.
 44. The device of claim 43 wherein said heated surface and said device are formed so that said heating of the heated surface by said source provides sufficient heat energy for sustaining said oscillation.
 45. The device of claim 44 wherein ambient cooling of said cooled surface provides sufficient cooling for sustaining the oscillation.
 46. The device of claim 43 wherein a structure comprising said heated surface is formed to absorb non-visible radiant energy from said source.
 47. The device of claim 46 wherein said structure is further formeD to spectrally absorb light from said source, whereby said illuminating light appears colored.
 48. The device of claim 46 wherein said structure scatters and diffuses light from said source.
 49. The device of claim 46 further including dichroic means for preferentially reflecting non-visible radiant energy from said source toward a piston of said structure for absorption and conversion into heat for heating said heated surface while preferentially transmitting visible radiant energy away from said structure for facilitating said illumination.
 50. The device of claim 46 wherein said heated surface comprises a thin, radiant energy absorbing coating on an internal wall of said structure for converting radiant energy from said source into heat directly adjacent said fluid to be heated.
 51. The device of claim 50 wherein said coating further is formed to reflect and diffuse radiant energy from said source.
 52. The device of claim 46 further including a reflective surface for reflecting radiant energy from said source into said structure for absorption and conversion into heat within said structure.
 53. The device of claim 46 further including a thermal insulator/partial reflector around the periphery of said structure for facilitating said heating and said illumination.
 54. The device of claim 26 wherein said alternate exposure of said fluid to the heated and cooled surfaces arises primarily at a result of the variation in chamber volume caused by the oscillating portions.
 55. The device of claim 1 further including means for heating the heated surface.
 56. The device of claim 55 wherein said surface is heated substantially independently of the instantaneous phase of the oscillating portion.
 57. The device of claim 1 wherein said chambers are made primarily of transparent materials to facilitate observation of the object and the internal structure of the device.
 58. The device of claim 1 wherein ambient cooling of said cooled surface provides sufficient cooling for sustaining the oscillation.
 59. The device of claim 1 wherein the oscillating portion comprises a free piston oscillating in a cylinder, bypass means bypassing a portion, and only a portion, of the axial length of the cylinder for positioning the center of oscillation of the free piston near the mid-point of the bypassed portion, said bypass means comprising an enlargement of the inside diameter of the cylinder in a region of the cylinder side-wall within said bypassed portion.
 60. The device of claim 59 wherein said bypass means provides a greater means separation between the piston and cylinder side-walls in the bypassed cylinder portion than in an adjoining portion of said cylinder.
 61. The device of claim 1 wherein the rebound chamber contains a fluid, means including the oscillation of the portion for sustaining motion of the rebound fluid, wherein the means for sustaining said relative motion of the object includes said motion of the rebound fluid.
 62. The device of claim 61 further including constriction means between said object and said oscillating portion to increase the velocity of the rebound fluid, whereby said relative motion of the object is augmented.
 63. The device of claim 61 wherein said motion of the rebound fluid is the primary means for sustaining said relative motion of the object.
 64. The device of claim 61 further including means for inducing substantially circuitous motion of the fluid in the rebound chamber.
 65. The device of claim 61 further including means for inducing substantially circuitous motion of the object in the rebound chamber.
 66. The device of claim 61 further including means for inducing rotational motion of the object in the rebound chamber. 